Corrosion inhibitor composition and method of using same



United States Patent 0 CORROSION INHIBITOR COMPOSITION AND METHOD OFUSING SAME Hugo Heimann, Kiryath Bialilr, and David Harry Kolm andYecheskel Israel, Haifa, Israel, assignors of onefourth to TechuionResearch and Development Foundation Limited, Haifa, Israel, a company ofIsrael No Drawing. Filed Feb. 1, 1957, Ser. No. 637,612

Claims priority, application Israel May 6, 1956 16 Claims. (Cl. 252148)This invention relates to pickles for the treatment of metal surfaces.

The usual pickles are aqueous solutions of mineral acids, or ofsubstances having an acid reaction or being capable of splitting offacids, which serve for cleaning metal surfaces by removing coatings orfilms of metal oxides, carbonates, sulfides or the like, or of oil or ofother impurities. As the acids or acidic substances are apt not only toremove the coating or film but also to affect the metal itself, they areusually admixed with inhibitors, i.e. substances that have the propertyof preventing the attack on the metal or, at least, to slow it down tosuch an extent that the operator can safely determine the correct timeof withdrawal of the metal from the pickling bath.

However, known icklin 'nhibitors have the desired effect on iron andsteel only and, even in that case, they have, in general to be used inrelatively high proportions. Known Pickling inhibitors have been foundto have virtually no protective effect in the case of metals which areeven more susceptible of being attacked by acids, such as alu um a zinc.

The present invention, therefore, has for its object to provide a picklemixture (which term will be used hereafter for the sake of brevity, forthe designation of pickles admixed with pickling inhibitors) capable ofuse for cleaning not only iron or steel surfaces, but also those ofother metals which are more readily attacked by pickling agents,especially aluminum and zinc.

The invention consists in pickle mixtures containing as picklinginhibitors at least one aromatic or araliphatic aldehyde, and at leastone basic nitrogen-containing aromatic compound.

In the context of this specification and the appended claims, the termaromatic includes, besides the aromatic hydrocarbon proper, alsoheterocyclic compounds of aromatic character, in accordance with theusage of modern textbooks of organic chemistry. (See, e.g. P. Karrer,Lehrbuch der org. Chemie, 1954.) Further, the term araliphatic aldehyde"is used to denote aliphatic aldehydes substituted by an aryl group,examples of such compounds being phenylacetaldehyde, cinnamaldehyde,etc.

The following aromatic aldehydes have been successfully used in carryingout the present invention:

Benzaldehyde Salicylaldehyde Vanillin Furfuraldehyde Phenylacetaldehydea-Naphthaldehyde Cinnamaldehyde Para-hydroxybenzaldehyde The followingnitrogen-containing aromatic compounds have been successfully used incarrying out the present invention:

Aniline Cinchonine Pyridine Cocaine Quinoline, Brucinc Nicotine drtfter168 hour 2,965,577 Patented Dec. 20, 1960 "ice The application of picklemixtures according to the invention are manifold. As examples there canbe cited: thi kjfgu fl mwigflfigt, e.g. aluminum ettles; the doom atio ouminum a d zinc surfaces prior to galvanic coating; the preparation ofclean aluminum and zinc surfaces prior to welding; the preparation ofextremely clean aluminum and zinc surfaces for chemical reactions inwhich these metals are required to have a reactive surface without anyoxide barrier; the protection of containers made from f aluminum or zincand containing either free acid, or substances which are able to split06 acids in the course i of time, from being attacked by these acids,etc.

The total proportion of the inhibitors in the pickle mixture, as well asthe relative proportions of the inhibitor components, must be adapted toindividual cases. On an average, mole of the aldehyde component and 0.01mole of the N-compound component, both per liter of pickle mixture, haveproved to be favorable.

The invention is illustrated in the following examples,

to which it is not limited. In these examples, strips of differentmetals -4 x 5 cms. in size were used and were treated at differenttemperatures and with different acids containing inhibitors inaccordance with this invention. In order to afford a proper basis forcomparison, control tests were carried out on strips of the same metals,using the same acids but in the absence of inhibitors. The control testswere as follows:

(1) Aluminum strips 4 x 5 cms. were immersed in hydrochloric acid of 10%strength, at room temperature; they were completely dissolved within 35minutes;

(2) Aluminum strips 4 x 5 cms. were immersed in 10% sulphuric acid; theydissolved slowly but, nevertheless, at a rate three times that obtainingwhen an inhibitor Example I The pickle mixture was composed of mls. ofaqueous hydrochloric acid of 10% strength by weight, 0.53 g. of a 40%aqueous nicotine sulfate solution, and 0.3 g. of benzaldehyde.

Into this solution an aluminum strip was submerged at 20 C. and thefollowing losses were observed:

I Mg. 2.2 17.1

After 24 hours Example 2 On repeating the same experiment at 40 C., thefollowing losses were observed:

Mg. After 1 hour 1.9 After 3 hour 4 Example 3 n submersion of analuminum strip into this solution at a temperature of 20 C., thefollowing losses were observed:

Mg. After 24 hour 3.6 After 168 hour 21 Example 4 0n repeating the lastexperiment at 40 C., the following losses were observed:

Mg. After 1 hour 3 After 3 hours 5 4 Example 5 On submersion of a in asolution prepared according to Example and at 20 C., the followinglosses were observed:

Mg. After 24 hours 6.5 After 168 hours 26.4

Example 6 The pickle m xture was composed of 100 ml. of hydrochloricacid solution of strength by weight, 0.53 g. of a 40% nicotine sulfatesolution and 0.27 g. of furfuraldehyde.

On submersion of an aluminum strip at a temperature of 20 C., thefollowing losses were observed:

Mg. After 24 hours 3.6 After 72 hours 14 Example 7 On repeating the lastexperiment at a temperature of 40 C., the following losses wereobserved:

Mg. After 1 hour 1.8 After 3 hour 4.4

Example 8 The pickle mixture was composed of 100 ml. of an aqueoushydrochloric acid solution of 10% strength by Weight, 0.36 g. ofcinchonine sulfate and 0.34 g. of phenylacetaldehyde.

On submersion into this solution of an aluminum strip at 20 C., thefollowing losses were observed:

Mg. .After 24 hours 3.2 After 72 hours 7.6

Example 9 On repeating the experiment according to Example 8 with a zincstrip, the following losses were observed:

Mg. After 24 hour 2.8 After 72 hour 7.1

Example 10 The pickle mixture was composed of 100 ml. of an aqueoushydrochloric acid solution of 10% strength by weight, 0.53 g. of a 40%aqueous nicotine sulfate solution. 0.3 g. of benzaldehyde and 0.5 g. offurfuraldehyde.

On submersion into this solution of an aluminum strip at a temperatureof 30' C., a loss of 30.0 mg. was observed after 96 hours.

Example 11 The pickle mixture was composed of 100 ml. of an aqueoushydrochloric acid solution of 15% strength by weight, 0.3 g. ofbenzaldchyde and 0.5 g. of a 40% aqueous nicotine sulfate solution.

On submersion into this solution of an aluminum strip at a temperatureof C., a loss of 26 mg. was observed after three days.

4 Example 12 The pickle mixture was composed of ml. of an aqueoussulfuric acid solution of 10% strength by weight, 0.3 g. of benzaldehydeand 0.36 g. of cinchonine sulfate.

On submersion into that solution of a zinc strip at a temperature of 20C., a loss of 11 mg. was observed after three days.

Example 13 By repeating the last experiment but using a 20% sulfuricacid solution, a loss of 9 mg. was observed after 24 hours.

Example 14 The pickling mixture was composed of 100 ml. of an aqueoushydrochloric acid solution of 10% strength by weight, 0.44 g.a-naphthaldehyde and 0.36 g. cinchonine sulfate.

On submersion into this solution of an aluminum strip at 20 C. for twodays, a loss of 6 mg. was observed, and after twelve days, the loss was28 mg.

Example 15 On repeating the experiment according to Example 14 with azinc strip, the following losses were observed:

Mg. After 2 days 6 After 12 days 15 After 30 days 62 it is possible toprepare inhibitor concentrates by dissolving the components in a commonsolvent. A few drops of such a concentrate are then added to the acidsolutions whenever needed.

Such concentrates may for example, be composed as follows:

15 g. of benzaldehyde 25 g. of nicotine sulfate 45 g. of methanol 15 g.of ethylacetate 15 g. of benzaldehyde 25 g. of nicotine sulfate 60 g. ofdimethylformamide 25 g. of a 40% aqueous nicotine sulfate solution 15 g.of benzaldehyde 60 g. of methylcellosolve which is the trade name of 2-mcthoxy ethanol or glycol monomethyl ether.

Although it appears that nicotine, cinchoninc and other alkaloids arevery suitable for the purposes of the present invention, it is notalways practical to use these sub stances on an industrial scale owingto their relatively high price. In such cases, other simpler and cheaperbasic N-compounds may be used, as illustrated in the following examples:

Example 16 The pickle mixture was composed of 100 ml. of an aqueoushydrochloric acid solution, 10% strength by weight, 0.3 g. benzaldehydeand 0.1 g. aniline.

0n submersion into this solution of an aluminum strip at 20 C. for threedays, a loss of 9.5 mg. was observed.

Example 17 important applications is the use of the inhibitors of thisinvention in the protection of aluminum aerosol containers-wherehydrolysis has been a real problem-and aluminum tubes and containers forother products which present a problem of corrosion.

We claim:

1. A pickle mixture for zinc and aluminum surfaces consistingessentially of an acid and, a hibitor, a $13 of at least one aldehydecompound selected from t group consisting of benzaldehyde,furfuraldehyde, phenyl acetaldehyde, alpha naphthaldehyde, and at leastone basic N-containing aromatic compound selected from the groupconsisting of nicotine, cinchonine, aniline, quinoline, and pyridine,the quantity used of each of said compounds being suflicient to preventcorrosion when used in combination.

2. A pickle mixture according to claim 1, in which the N-compound isnicotine.

3. A pickle mixture according to claim 1, in which the N-compound iscinchonine.

4. A pickle mixture according to claim 1, in which the N-compound isaniline.

5. A pickle mixture according to claim 1, in which the N-compound isquinoline.

6. A pickle mixture according to claim 1, in which the N-compound ispyridine.

7. A pickle mixture according to claim 1, in which the aldehyde isbenzaldehyde.

8. A pickle mixture according to claim 1, in which the aldehyde isfurfuraldehyde.

9. A pickle mixture according to claim 1, in which the aldehyde isphenyl-acetaldehyde.

10. A pickle mixture according to claim 1, in which the aldehyde isa-naphthaldehyde.

11. A corrosion inhibitor composition for add'tion to aqueous solutions,capable of causing acidic corrosion to zinc and aluminum surfaces,consisting essentially of a mixture of at least e aldehyde compoundselected from the group consisting of Benzaldehyde, furfuraidehyde,phenyl acetaldehyde, alpha naphthaldehyde, agd Lge t one basicN-containi atic compound selected rom the group consisting of nicotine,conchonine, aniline, quinoline, and pyridine, the quantity used of eachof said compounds being suflicient to prevent corrosion when used incombination.

12. The method of pickling surfaces of metals selected from the groupconsisting of aluminum and zinc which comprises the step of: subjectingthe metal to a bath containing an acid and an inhibitor consisting of amixture of at least one aldehyde compound selected from the groupconsisting of benzaldehyde, furfuraldehyde, phenyl acetaldehyde, alphanaphthaldehyde, and at least one basic N-containing aromatic compoundselected from the group consisting of nicotine, cinchonine, aniline,quinoline and pyridine, the quantity used of each of said compoundsbeing suflicient to prevent corrosion when used in combination.

13. A method according to claim 12, wherein the metal surfaces comprisealuminum.

14. A method according to claim 12, wherein the metal surfaces comprisezinc.

15. An aerosol container formed of a material containing a metalselected from the group consisting of zinc and aluminum, containingtherein a composition normally corrosive to said material, and aninhibitor consisting of a mixture of at least one aldehyde compoundselected from the group consisting of benzaldehyde. furfuraldehyde,phenyl acetaldehyde, alpha naphthaldehyde, and at least one basicN-containing aromatic compound selected from the group consisting ofnicotine, cinchonine, aniline, quinoline and pyridine, the quantity usedof each of said compounds being sufiicient to prevent corrosion whenused in combination.

16. An aerosol'container according to claim 15, wherein there is usedabout 0.03 mole of the aldehyde and about 0.01 mole of the basicN-containing aromatic com pound per litre of the product.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Corrosion Handbook by Uhlig, pp. 910,

911, pub. by John Wiley & Sons, Inc., NY. (1948).

11. A CORROSION INHIBITOR COMPOSITION FOR ADIDTION TO AQUEOUS SOLUTIONS,CAPABLE OF CAUSING ACIDIC CORROSION ZINC AND ALUMINUM SURFACES,CONSISTING ESSENTIALLY OF A MIXTURE OF AT LEAST ONE ALDEHYDE COMPOUNDSELECTED FROM THE GROUP CONSISTING OF BENZALDEHYDE, FURFURALDEHYDE,PHENYL ACETALDEHYDE, ALPHA NAPHTHALDEHYDE, AND AT LEAST ONE BASICN-CONTAINING AROMATIC COMPOUND SELECTED FROM THE GROUP CONSISTING OFNICOTINE, CONCHONINE, ANILINE, QUINOLINE, AND PYRIDINE, THE QUANTITYUSED OF EACH OF SAID COMPOUNDS BEING SUFFICIENT TO PREVENT CORROSIONWHEN USED IN COMBINATION.